Press Release

July 16, 2015

Fisheries Research Agency

The relationship between harmful algal blooms in the Yatsushiro Sea and preceding meteorological conditions has been identified

  • We have shown that the occurrence of Chattonella blooms in the Yatsushiro Sea is associated with temperature from winter to spring and the start timing of the rainy season.
  • Chattonella blooms tend to occur in years that have high average air temperature for the period between February and April (AMeDAS: Yatsushiro) or have a relatively late timing of the rainy season in southern Kyushu, and most large-scale bloom years met both of these conditions.

Chattonella is harmful plankton that kills fish and shellfish by frequently forming blooms along the Japanese coast in summer. In the Yatsushiro Sea located in western Kyushu, large-scale blooms occurred in 2009 and 2010, causing ¥8 billion in damage to the aquaculture industries.

To clarify the environmental conditions for the occurrence of Chattonella blooms, we analyzed the data of Chattonella blooms and meteorological conditions from January to June for a 25-year period between 1988 (the first year when Chattonella bloom occurred in the Yatsushiro Sea) and 2012 to extract meteorological factors associated with the occurrence of blooms. The occurrence date of Chattonella blooms significantly correlated to the average air temperature for the February-April period (AMeDAS: Yatsushiro) and the onset date of the rainy season in southern Kyushu, with these two meteorological factors showing significant differences between occurrence and non-occurence years of Chattonella blooms. More specifically, Chattonella blooms tend to occur in years that have high average air temperatures for the period between February and April or have a relatively late timing of the rainy season in southern Kyushu, and most large-scale bloom years met both of these conditions.

To reduce damage to fisheries, it is important to predict the occurrence of Chattonella blooms as early as possible. These findings, albeit basic ones, are meaningful in that the relationship between easily accessible meteorological data and the occurrence of blooms has been identified. In the future, by incorporating the analysis of the oceanographic conditions, we hope to elucidate the mechanisms for the occurrence of Chattonella blooms in the Yatsushiro Sea and develop prediction technologies.



Fig.1 Micrograph of Chattonella



Fig. 2 Relationships between the occurrence of Chattonella blooms and the average air temperature from February to April (AMeDAS: Yatsushiro) and the onset date of the rainy season in southern Kyushu